why does normal use have to do the seats any harm?? you just need to get in and out sensibly/carefully.. It's only careless use that does any harm.
I sold a 92 SRi cav last year that i'd had for years and used every day, same style seats as the RS recaro's - loads you see are fooked, but the interior in mine was like new, literally, after 12 years and 170,000 miles. Just don't lean/rub on the side back bolster or sit on the side seat bolster when you get in and out

Seems kinda mad to me to have the most supportive seats you'll ever find in a car then stick a shonky old nylon cover on it to slide around on??
Bit like covering the car in masking tape to stop the stonechips - use it sensibly, or leave it in the garage so nothing wears out..